Printed in Great Britain 0021-8502/00/ $- see front matterPII: S0021-8502(00)00017-3 COLLECTION OF FUNGAL SPORES ON AIR FILTERS AND SPORE REENTRAINMENT FROM FILTERS INTO AIR

Abstract*The collection of fungal spores on ventilation "lters and their potential for subsequent reentrainment were compared with the collection and reentrainment of standard test particles. Potassium chloride (KCl) particles were selected as the standard test particles, as recommended by the ASHRAE standard 52.2. Penicillium brevicompactum and Penicillium melinii were selected to represent common fungal spores in indoor air. Two commonly used "lters were tested: medium-e$ciency "lter medium A from a pre"lter and higher e$ciency medium B from a "ne "lter. The collection e$ciencies of "lters were determined at a face velocity to the pleated "lter assembly of 2.54 m s~1, which is typical for both "lters. The collection e$ciency was found to be slightly lower for fungal spores than for KCl particles of the same aerodynamic size. When the reentrainment velocity was the same as the loading velocity through the "lter medium (0.56 m s~1 for A, 0.09 m s~1 for B), the reentrainment rate was less than 0.4%. When the reentrainment velocity was increased to 3.00 m s~1, the reentrainment of fungal spores was higher than that of KCl particles: 2}6 % for P. brevicompactum, 5}12 % for P. melinii, and 0.2}0.6 % for KCl particles. The di!erences in behaviour between fungal spores and KCl particles were attributed to aggregation and deaggregation of fungal spores. The higher reentrainment rate of P. melinii compared to that of P. brevicompactum can b